Dual laminated telephone cable sheath



May 23, 1967 o. G. GARNER 3,321,572

DUAL LAMINATED TELEPHONE CABLE SHEATH Filed Sept. 13, 1965 ATTORNEYS.

United States Patent 3,321,572 DUAL LAMINATED TELEPHONE CABLE SHEATH Oscar G. Garner, Westfield, N..ll., assignor to General Cable Corporation, New York, N.Y., a corporation of New Jersey Filed Sept. 13, 1965, Ser. No. 486,863 7 Claims. (Cl. 174-105) This invention relates to electric cables and more especially to pulp or paper tape insulated telephone cables.

It is an object of the invention to provide a telephone cable sheathing that is more reliable, as far as moisture resistance and gas tightness are concerned; even if the outermost jacket is` punctured by lightning or damaged by rodents and at the same time achieve this with a reduction in the overall diameter of the cable. j

Another object is to eliminate the need or use of the present conventional sheathing, the so-called St-alpeth sheathing, which consists of an outer plastic jacket and a laminated metallic sheath of tinned steel and aluminum with the edges of the tinned steel being soldered, and replacing this with a triple jacket construction consisting of an outer plastic jacket, an intermediate jacket formed from an adhesive polyethylene-aluminum-adhesive polyethylene laminate, known as FPA or fused aluminumpolyethylene tape, and an inner jacket formed from a polyester-aluminum foil-adhesive polyethylene laminate, known as a thin-skin jacket.

Both, the intermediate and the inner jackets are sealed. The intermedia-te jacket by the method disclosed in the copendiug Garner application Ser. No. 427,435 and the inner jacket by the method described in the Jachimowicz U.S. Patent No. 3,206,541, both assigned to the assignee of the present application. The tapes used for the intermediate and the inner jackets have about the reversed ratio of metal to plastic; with the intermediate jacket having more met-al and the inner jacket more plastic. The two sealed inner jackets give a greater reliability to this sheathing than the soldered inner jacket of the Stalpeth sheathing. This permits a reduction in the outermost plastic jacket of this triple jacke-ted construction, resulting in an overall reduction of the cable diameter. This is a significant advantage both for overhead or underground use.

Other objects and features relate to the longitudinal seams of the tape, to their correlation with one another and to the bonding of some layers and the prevention of bonding of other layers in order to produce the improved cable of this invention.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing forming a part hereof in which like reference characters indicate corresponding parts of all the views:

FIGURE 1 is a diagrammatic view showing the Way in which the cable of this invention can be manufactured;

FIGURE 2 is a greatly enlarged sectional view through the cable made in accordance with the method and apparatus shown in FIGURE 1;

FIGURES 3 and 4 are greatly enlarged, fragmentary sectional views taken on the lines 3-3 and 4-4 of FIG- URE l;

FIGURE 5 is a greatly enlarged detail view of the area 5 5 of FIGURE 2; and

FIGURES 6 and 7 are greatly enlarged views of the areas 646 and 7 7, respectively, of FIGURE 2.

FIGURE 1 shows a cable core 10 consisting of a plurality of conductors individu-ally insulated with pulp or paper ribbon assembled into a core around which are wrapped core tapes 12, usually two paper tapes each S mils in thickness. An inner jacket or tape 14 is formed progressively around the Wrapped core 10 as the core advances continuously in the direction indicated by the arrow 15. The tape 14 is preferably a sandwich sheath having a laminated construction consisting of a thin metallic foil 16 to the opposite sides of which are securely bonded plastic coatings 18 and20 (FIG. 3). The construction of this tape or sleeve 14 will be described more fully in connection with FIGURE 5.

For the presen-t it is suiiicient to understand that the coating 18 is a heat-scalable polyolefin coating and prefer-ably a copolymer of polyethylene modified by monomers containing reactive carboxyl groups which cause the coating to chemically bond to the metal surface of the foil 16.

The outer coating 20 is preferably chemically bonded to the foil 16 but made of a different plastic which has a higher softening point that the inner coating 18. This outer coating 20 may be made of polyethylene terephthalate Mylan As the tape 14 is formed around the core 10, the edge portions of the tape are bent up to form radially extending tabs 22. The longitudinal seam of the jacket or tape 14 passes through a heating station 24 where jets of hot gas 27 impinge against the coating 18 on the confronting faces of the tabs 22 and raise the temperature of the coating 18 to its softening or melting point so that the tabs are heat sealed to one another when they pass between pinch rolls 28 just beyond the heating station 24. The plastic coating 18 may be exposed to gas flame heated to 800 degrees F. and the tabs 22 are preferably at least mils long to provide an elongated seam which is highly resistant vto moisture penetration along the entire length of the cable. Beyond the feed rolls 28, the radially extending seam is then folded over by passing the cable through a folding station 30` which presses t-he tabs down into a lgenerally cylindrical configuration as shown in FIGURE 2. This folding operation is performed by a ring 32 at the folding station 30 of FIGURE 1 and it leaves the tabs generally parallel to the adjacent surface of the circumferential portion of the jacket or tape 14 over which the tabs are folded.

An outer jacket or tape 34 is formed progressively around the inner jacket or tape 14 beyond the folding station 30 as illustrated in FIGURE l. This outer tape has a laminated construction with a metal strip considerably thicker than the foil in the tape 14, and with plastic coating on both sides, preferably chemically vbonded to the metal. The outer tape 34 is formed with a lap seam and is subjected to heat by a heater 36 at a second heating station 38, which raises the coatings on the overlapped portions of the tape at the seam to a heat sealing temperature.

The cable is then completed Iby passing it through an extruder 40y which eXtrudes an outer sheath 42 over the -outer tape 34. This outer sheath 42 is preferably polyethylene.

FIGURE 2 shows the construction of the completed cable but the scale in FIGURE 2 is not large enough to illustrate the plastic coatings without exaggerating the thickness so much as to show parts completely out of proportion. For detailed illustration of the construction, and the plastic coatings, three detail Views, FIGURES 5, 6 and 7, are shown as enlargements of the structure in FIGURE 2 `at the areas 55, 6-6 and 7-7, respectively.

FIGURE 5 shows the core conductors with the intercalated tapes 12 covered by the inner tape 14 which is preferably made with an aluminum, copper or steel metal foil 16 between .1 and l mil in thickness. The plastic coating 18 on the inside of the tape 14 is preferably between l and l0 mils in thickness. The outer coating 20 may have a thickness within this same range. The tape 14 its loosely over the core 10 and is preferably not bonded to the core tape 12. This results in a more flexible cable.

Outside of the tape 14 there is an outer tape 34 which is preferably made of metal strip 48 such as aluminum or copper having a thickness of'approxirnately 8 mils, or within a range of 6-12 mils,

The tape 34 has an inner plastic coating 50 and an outer plastic coating 50. These coatings are preferably of the same material as the inner coating 18 of the tape 14 so that when the overlapping edges of the outer tape 34 are heated the plastic coating of the confronting faces of these overlapping edges will bond the edges together to provide a moisture-tight seal. Each coating 50 is preferably about 2 mils thick.

Thus the ratio of plastic to metal may be about eight to one for the inner jacket, but about one to two for the intermediate jacket.

Overlapping edges 52 and 53 of the outer tape 34 are shown in FIGURE 7. The extent of the overlapping of these edges 52 and 53 should be sufficient to produce a moisture-proof seal and experience has shown that onequarter to three-eighths inch overlap is effective for this purpose.

It is desirable that the outer tape 34 4is not bonded to the inner tape 14. This is the reason for having the outer coating 20 of the inner tape 14 made of material which will not soften and seal to the coating of the outer tape 34 when the overlapping edges of the outer tape are heated to form the seal along the seam of the outer tape.

FIGURE 6 shows the detailed construction of the cable at the region of the seam of the inner jacket or tape 14; and FIGURE 7 shows the seam for the outer tape. It is a feature of the invention that these seams are located `at angularly spaced regions around the circumference of the cable.

The outer sheath 42 is extruded in the conventional way and has a radial thickness between 60 and 125 mils. This outer sheath is preferably made of polyethylene.

The preferred embodiment of the invention has been illustrated and described, but changes and modifications can be made, and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. A small diameter telephone cable having overlying sealed jackets unbonded to each other and an outer sheath bonded to the outermost jacket, said cable comprising a number of individually insulated conductorsstranded into a core, a wrapping of paper tapes surrounding the cable core, over the wrapped core an inner jacket formed from a longitudinally folded tape including a metal foil with at least its inside surface covered with a plastic coating that is chemically bonded to the metal foil, the tape having edge portions that are bent outwardly in juxtaposition and bonded together into a seam, the bonded edge portions being folded down against the inner jacket, an intermediate jacket formed from a laminated tape comprising a metal strip thicker than the metal foil coated on both sides with heat-sealing plastic chemically bonded to the metal strip, the tape forming said intermediate jacket being folded longitudinally around over the inner jacket and having a lap seam which is sealed by the bonding of the plastic on the inside yof the outer overlapping edge portion to the plastic on the outside of the inner overlapping edge portion, the seams of the inner jacket and the intermediate jacket being spaced angularly from each other around the-circumference of the cable, the intermediate jacket fitting closely over the inner jacket, but not bonded to the inner jacket, and a plastic outer sheath surrounding the outside of the intermediate jacket and bonded to the plastic over the outside surface of the intermediate jacket to further seal the lap seam.

2. The cable described in claim 1 characterized by the tapes of the inner and the intermediate jackets having about the reversed ratio of metal to plastic, the inner jacket having more plastic and the intermediate jacket having more metal.

3. The cable described in claim 1 characterized by a plastic on the outside of the inner jacket being of different material from the plastic coating on the inside of the inner jacket and having a softening point at a substantially higher temperature than that of the plastic on the inside yof the inner jacket.

4. The cable described in claim 1 characterized by the metal of the inner jacket being of substantially less thickness than that of the intermediate jacket, and the metal component of one of the jackets being steel and providing magnetic shielding for the insulated conductors of the core.

5. The cable described in claim 4 characterized by the metal of the inner jacket being steel and of a thickness between .l and l mil, and the metal of the intermediate jacket being a different metal and of a thickness between 4 and 12 mils.

6. The cable described in claim 1 characterized by both tapes used to form the inner and intermediate jackets being coated on both sides by -plastic chemically bonded to the surfaces of the tape, the inner surface of the inner tape being bonded with a low melting polyolen and the outer surface of the inner tape being coated with a higher melting point plastic of the class consisting of high density polyethylene, polypropylene, and a polyethylene terephthalate, both sides of the intermediate jacket being coated with a polyolein copolymer and the outer sheath or jacket being made of polyethylene bonded to the intermediate jacket.

7. The cable described in claim 1 characterized by the cable containing a plurality of conductors with electrical insulation from the group consisting of pulp and ribbon paper insulation, the inner jacket being applied over the core and having a thickness between 2.1 `and 11 mils, and the intermediate jacket having a thickness between 10 and 16 mils and the sheath having a radial thickness of between 20 and 125 mils.

References Cited by the Examiner UNITED STATES PATENTS 3,206,541 9/ 1965 Iachimowicz 174-107 3,233,036 2/1966 Jachimowicz 174-36 X FOREIGN PATENTS 968,061 8/ 1964 Great Britain.

LEWIS H. MYERS, Primarj7 Examiner.

L. E. ASKIN, Examiner.

H. HUBERFELD, Assistant Examiner. 

1. A SMALL DIAMETER TELEPHONE CABLE HAVING OVERLYING SEALED JACKETS UNBONDED TO EACH OTHER AND AN OUTER SHEATH BONDED TO THE OUTERMOST JACKET, SAID CABLE COMPRISING A NUMBR OF INDIVIDUALLY INSULATED CONDUCTORS STRANDED INTO A CORE, A WRAPPING OF PAPER TAPES SURROUNDING THE CABLE CORE, OVER THE WRAPPED CORE AN INNER JACKET FORMED FROM A LONGITUDINALLY FOLED TAPE INCLUDING A METAL FOIL WITH AT LEAST ITS INSIDE SURFACE COVERED WITH A PLASTIC COATING THAT IS CHEMICALLY BONDED TO THE METAL FOIL, THE TAPE HAVING EDGE PORTIONS THAT ARE BENT OUTWARDLY IN JUXTAPOSITION AND BONDED TOGETHER INTO A SEAM, THE BONDED EDGE PORTIONS BEING FOLDED DOWN AGAINST THE INNER JACKET, AN INTERMEDIATE JACKET FORMED FROM A LAMINATED TAPE COMPRISING A METAL STRIP THICKER THAN THE METAL FOIL COATED ON BOTH SIDES WITH HEAT-SEALING PLASTIC CHEMICALLY BONDED TO THE METAL STRIP, THE TAPE FORMING SAID INTERMEDIATE JACKET BEING FOLDED LONGITUDINALLY AROUND OVER THE INNER JACKET AND HAVING A LAP SEAM WHICH IS SEALED BY THE BONDING OF THE PLASTIC ON THE INSIDE OF THE OUTER OVERLAPPING EDGE PORTION TO THE PLASTIC ON THE OUTSIDE OF THE INNER OVERLAPPING EDGE PORTION, THE SEAMS OF THE INNER JACKET AND THE INTERMEDIATE JACKET BEING SPACED ANGULARLY FROM EACH OTHER AROUND THE CIRCUMFERENCE OF THE CABLE, THE INTERMEDIATE JACKET FITTING CLOSELY OVER THE INNER JACKET, BUT NOT BONDED TO THE INNER JACKET, AND A PLASTIC OUTER SHEATH SURROUNDING THE OUTSIDE OF THE INTERMEDIATE JACKET AND BONDED TO THE PLASTIC OVER THE OUTSIDE SURFACE OF THE INTERMEDIATE JACKET TO FURTHER SEAL THE LAP SEAM. 